Businesses and individuals rely upon the Internet and various communications networks for exchanging data electronically. Computers, personal digital assistants, and other types of mobile communication devices coupled to the Internet, enable users to readily gain access to and exchange data of all types (e.g., sound, text, numerical data, video, graphics, multi-media, emails, etc.) with other computers, databases, websites, etc. Now, users can participate in live discussions in chat rooms, play games in real-time, watch streaming video, listen to music, shop and trade on-line, download files, etc. And given the requisite bandwidth, it is possible to provide video-on-demand, HDTV, IP telephony, video teleconferencing, and other types of bandwidth intensive applications.
At the core of networking technology lies the fundamental proposition of digitizing the data into a string of bits comprised of one's and zero's. The digital data is divided into groups known as “packets.” Embedded within each packet are various addresses mandated by an Internet Protocol (IP). These IP addresses are analogous to a postal letter's return address and recipient address in that the IP addresses provide information on how the packets are to be forwarded. Routers coupled to various nodes of the network, examine the packets and route the packets based on their IP addresses. During transmission, a packet can be routed via multiple intermediary routers before reaching its final destination. In this manner, packets are separately transmitted and routed through the network until they eventually reach their intended destination.
Each time a router examines a packet and subsequently routes the packet to a different location, it must first essentially modify that packet. Specifically, the router must modify the Destination Address (DA), the Source Address (SA), the Time-to-Live (TTL), and the Checksum. One way by which this is commonly done today entails the use of software. A computer program takes the packet, modifies it, and then sends out the modified packet. Although this software approach is straightforward, it is relatively time intensive. Given that routers are being designed to route millions of packets per second, even the slightest incremental delay incurred while routing a packet can result in severe aggregate performance degradation.
In an effort to improve performance, some router manufacturers have implemented hardware designs. Rather than running software on a generic processor, these manufacturers have customized circuitry specifically designed to handle the requisite packet modifications. The specialized hardware reads the old values, computes the new values, writes the new values back to the packet memory, and then sends the modified packet out. One disadvantage to this hardware approach is that the additional circuitry increases complexity and resultant cost. Additional die space is necessary to fabricate the hardware design. A bigger chip directly translates into increased production costs. Furthermore, rewriting the packet memory prior to the packet being sent, requires the addition of more write ports or packet buffers to temporarily hold the packet data. This adds to the complexity and cost. And although the packet modifications can be computed on-the-fly by hardware, the associated latency can detrimentally impact its performance. Of course, this latency can be effectively masked through the use of pipelining techniques. However, the trade-off is that pipelining entails additional logic which, in turn, leads to increased production cost. This is especially the case with using pipelining to modify packets; a deep pipeline is needed in order to compute the Checksum because the Checksum must cover the entire portion of the packet being modified. Deep pipelines consume valuable chip space and can significantly increase the cost of the router.
Therefore, there are various disadvantages inherent to the prior art networking methods used to modify packets in routing.